4 ms·

some people testing KFm on a large rc I found now while looking for info on the airfoil itself https://www.youtube.com/watch?v=6H-s7yuJcwk https://www.youtube.c

some people testing KFm on a large rc I found now while looking for info on the airfoil itself https://www.youtube.com/watch?v=6H-s7yuJcwk https://www.youtube.com/watch?v=6H-s7yuJcwk it's interesting. too bad I couldn't find any video in a wind gallery. (edit: did my own, not the best software but it's something https://i.imgur.com/TudMHlX.png https://i.imgur.com/TudMHlX.png - there's some lift in there to be had) Ultimately I'm still unconvinced it works the way they tell it works.

semi-extrinsic 8y ago
There's been actual research (incl. by NASA) on the KFm foil (although scaled up for real airplanes or military drones) which has come up inconclusive. Just FYI, your simulation looks really underresolved and the leading edge of the foil should be rounded off. Not intended as criticism, just in case you want to improve. If you do proceed to work on this, which I think would be interesting as KFm in the RC wing size regime seems not so well studied: avoid vortex panel method and anything else based on inviscid/potential theory, you're interested in laminar flow for RC applications. I'd give it a try e.g. with SU2 starting from the laminar flow around cylinder tutorial, and making you own mesh file for the KFm with gmsh (pretty easy to use mesher with GUI): https://su2code.github.io/tutorials/Laminar_Cylinder/ https://su2code.github.io/tutorials/Laminar_Cylinder/ http://gmsh.info http://gmsh.info
- LoSboccacc 8y ago
  thanks for the pointers! I'm way out of my element here and just thrown together something with the first software I found on internet. about this: > the leading edge of the foil should be rounded off I agree, however, in the first round of simulations the leading and trailing edge where they themselves giving a lot of lift to the foil (especially the trailing tapering), so in my naivety I slabbed both edges to reduce those effects and see if the flow was deflected by the slab alone. interestingly, even if the model itself is flawed and the simulation technicalities off for the intended purposes, having the slab slightly forward gave also interesting results, almost the same lift and a lot less drag 1) https://i.imgur.com/TudMHlX.png https://i.imgur.com/TudMHlX.png 2) https://i.imgur.com/GjiVL8s.png https://i.imgur.com/GjiVL8s.png so I came up with an idea for a foil that's still easy to craft out of foam or balsa and does use the different effects do redirect the flow more effectively 3) https://i.imgur.com/n9RUHs5.png https://i.imgur.com/n9RUHs5.png of course all of this is purely based of a low resolution simulation, still, it was fun. I've no chance to test them in practice tho.
  - semi-extrinsic 8y ago
    Interesting stuff! What you need to be careful about when comparing different foils is to ensure you compare at the same angle-of-attack (AoA). Especially the latter foil has a high "intrinsic" AoA. The best way to do it is running simulations that span a range of AoA, calculating lift and drag for each one, and setting the reference for each foil at the zero lift AoA. Then you can do a fair comparison.

semi-extrinsic 8y ago

There's been actual research (incl. by NASA) on the KFm foil (although scaled up for real airplanes or military drones) which has come up inconclusive. Just FYI, your simulation looks really underresolved and the leading edge of the foil should be rounded off. Not intended as criticism, just in case you want to improve. If you do proceed to work on this, which I think would be interesting as KFm in the RC wing size regime seems not so well studied: avoid vortex panel method and anything else based on inviscid/potential theory, you're interested in laminar flow for RC applications. I'd give it a try e.g. with SU2 starting from the laminar flow around cylinder tutorial, and making you own mesh file for the KFm with gmsh (pretty easy to use mesher with GUI): https://su2code.github.io/tutorials/Laminar_Cylinder/ https://su2code.github.io/tutorials/Laminar_Cylinder/ http://gmsh.info http://gmsh.info

LoSboccacc 8y ago
thanks for the pointers! I'm way out of my element here and just thrown together something with the first software I found on internet. about this: > the leading edge of the foil should be rounded off I agree, however, in the first round of simulations the leading and trailing edge where they themselves giving a lot of lift to the foil (especially the trailing tapering), so in my naivety I slabbed both edges to reduce those effects and see if the flow was deflected by the slab alone. interestingly, even if the model itself is flawed and the simulation technicalities off for the intended purposes, having the slab slightly forward gave also interesting results, almost the same lift and a lot less drag 1) https://i.imgur.com/TudMHlX.png https://i.imgur.com/TudMHlX.png 2) https://i.imgur.com/GjiVL8s.png https://i.imgur.com/GjiVL8s.png so I came up with an idea for a foil that's still easy to craft out of foam or balsa and does use the different effects do redirect the flow more effectively 3) https://i.imgur.com/n9RUHs5.png https://i.imgur.com/n9RUHs5.png of course all of this is purely based of a low resolution simulation, still, it was fun. I've no chance to test them in practice tho.
- semi-extrinsic 8y ago
  Interesting stuff! What you need to be careful about when comparing different foils is to ensure you compare at the same angle-of-attack (AoA). Especially the latter foil has a high "intrinsic" AoA. The best way to do it is running simulations that span a range of AoA, calculating lift and drag for each one, and setting the reference for each foil at the zero lift AoA. Then you can do a fair comparison.